The present invention relates to a method and apparatus for determining the quantity of copying light during reproduction of images on color originals, especially color photographic negatives, onto photosensitive material. More particularly, the invention relates to improvements in a method and apparatus for ascertaining appropriate quantities of light in the primary colors during reproduction of images on color originals onto photographic paper on the like. Still more particularly, the invention relates to a method and apparatus for ascertaining the quantities of copying light in several colors on the basis of evaluation of so-called test exposures which are provided on the originals outside of the image bearing areas.
U.S. Pat. No. 2,269,161 to Morse discloses a method of reproducing a multicolored photograph which includes preparing by the same process, with identical materials and under identical processing conditions, an approximately neutral color photographic record of a neutral colored light of known spectral distribution, noting the departure of the record from the neutral color, duplicating the photograph, and controlling the relative amounts of the primary colors in the duplicate in accordance with the amount of departure. The patented method is intended to compensate for color departures of the record from neutral colored light. It has been found that this method fails to insure the making of satisfactory reproductions (a) when the original was exposed to light other than that which is best suited for the making of acceptable exposures (a typical example is a daylight film which was exposed in artificial light or vice versa), and (b) when the condition of latent images changes during the interval which elapses between exposure and development.
For example, an exposure which was made shortly before sundown will be too red. On the other hand, an exposure which is made on a cloudy day is likely to contain excessive amounts of blue light.